1. Field of the Invention
This invention relates to defoamers for pulp and paper mill applications based on natural renewable materials and synthetic oils.
2. Description of Related Art
Defoamers (or antifoams) are being used extensively in pulp and paper mill. Four factors contribute to foam generation: a liquid medium (such as water), chemically conducive agents (such as surface-active materials), a source of air, and mechanical energy. Pulp and papermaking systems have water in abundance, have many chemicals both intrinsic to wood and extrinsic due to processing chemicals, and entail much mechanical energy, such as water agitation, washing and thickening processes combining to result in the formation of foam. For example, in the washing of pulp in Kraft mills, foam is generated in black liquor, which is among the most difficult to defoam. Other pulp and paper applications of defoamers include their use in sulfite pulping process and in effluent and other water treatment.
Many defoamers have been employed for these applications. In the past, Kerosene has been used as a defoamer. Later defoamers include hydrocarbon oil or silicone oil, frequently containing hydrophobic particles in them Because of economic, environmental, and quality issues, it is desirable to decrease the use of hydrocarbon and silicone oil. The employment of triglyceride oils may be particularly attractive in this context because they are perceived to be less toxic and more “green.”
There is still a need in the industry to find better foam control composition that works well in pulp and paper applications. It is desirable to have a foam control composition that remains stable before use and stays effective in the pulp or papermill environment.